Traveling chain mechanisms, such as those disclosed in U.S. Pat. No. 5,201,688, issued Apr. 13, 1993, and assigned to the assignee of the present invention, have a traveling member disposed around a sprocket radially inward of an endless chain trained around the spaced sprockets. The traveling member increases the effective diameter of the sprocket thereby affecting the drive ratio between the sprockets. The sprockets have the same diameter and therefore the traveling chain member will change the ratio from an under drive to an overdrive between input and output sprockets, depending upon which sprocket is currently supporting the traveling member.
To transfer the chain from one sprocket to another, a derailer mechanism, such as that shown in U.S. Pat. No. 5,180,341, issued Jan. 19, 1993, and assigned to the assignee of the present invention, is provided at each sprocket to release the traveling chain member. The derailer mechanism shown in the above patent includes a flexible plate member which has apertures in which the pins of each link of the traveling chain are entrapped. When the plates are separated or spread, the pins are released and the centrifugal action throws the lead link radially outward to engage a guide member which directs the traveling chain to the other sprocket.
The traveling chain has inner teeth which mesh with the sprockets and outer teeth which mesh with the endless chain. Thus, the traveling chain is driven by the endless chain during travel between the sprockets.